Currently scintimammography imaging to detect breast cancer is performed with standard nuclear medicine cameras and it suffers from poor sensitivity for lesions under about 1 cm in diameter and lesions located in the medial aspect of the breast, away from the large camera surface. The main contributing factor to this poor performance is the poor spatial resolution during imaging due to the relatively large distance between the lesion and the collimator of the detector head.
The development of compact small field of view (FOV) cameras/detectors, allowed for the placement of the camera directly against the breast thus significantly minimizing spatial resolution effects by minimizing the target to collimator distance. Testing and evaluation of these small FOV cameras in direct contact with the breast provided the expected increase in detection sensitivity for small lesions. However it was apparent that lesion-to-camera distance still had a strong impact upon lesion detection and even these dedicated instruments can show substantial sensitivity variation depending on lesion position within the breast. By incorporating a second camera/detector on the opposite side of the breast, total target-to-detector distance was further minimized.
In 2001, Majewski et al. (S. Majewski, E. Curran, C. Keppel, D. Keiper, B. Kross, A. Pulumbo, V. Popov, A. G. Weisenberger, B. Welch, R. Wokjcik, M. B. Willimas, A. R. Goods, M. Moore, and G. Zheng, Optimization of Dedicated Scintimammography Procedure Using Detector Prototypes and Compressible Phantoms, IEEE Trans. Nucl. Sci, vol 48, no. 3, pp 822-829, June 2001) proposed a system implementing two identical and opposed detector heads placed on either side of a breast under compression to provide an optimal imaging geometry. While this improved approach confirmed that the dual head system is especially useful in most clinical situations where lesion location is not known a priori, the remaining important issue was how to combine most efficiently the two images obtained from the double sided imaging.
In a paper published in 2002, Kieper et al. (D. Kieper, S. Majewski, V. Popov, M. F. Smith, A. G. Weisenberger, B. Welch, R. Wojcik, M. B. Williams, M. J. Moore, and D. Narayanan, “Improved Lesion Visibility in a Dedicated Dual-Head Scintimammography System—Phantom Results”, submitted for publication at the 2002 IEEE Medical Imaging Conference, Norfolk, Va., Nov. 7-19, 2002) further proposed to enhance lesion detection and localization by enhancing the contrast value through the application of a geometric mean technique involving the use of the square root of two registered images, one from each of the two cameras used to compress the breast from opposing sides. This technique further enhanced lesion vs. background contrast, but still did not produced the degree of contrast desired.
Accordingly, there remains a need to further enhance lesion vs. background contrast to more accurately characterize and localize potentially cancerous lesions.